The known telescopes, binoculars and microscopes have apertures and diaphragms. For these reasons the user's visual field is small even with minor magnification. For example, common binoculars for theatre goers have a small visual field of 200 m for a 1000 m distance, i.e. an angle of view of only about 11. The stronger the magnification, the smaller is the visual field.
Furthermore, telescopes are to be held and adjusted by hand to assure that the observer's eyes in fact see the desired objects. When looking through telescopes only the central areas of the human retina are used, which are responsible for sharp, clear vision. The remaining very large retinal areas, which are responsible for visual perception of motion, are not used when looking through a telescope.
Known afocal lenses are convex-concave lenses of considerable thickness having spherically curved front and rear surfaces, the front surface curvature being lower in comparison to the rear surface curvature, following well-known optical laws. By definition afocal lenses are lenses without a focal point, which means that parallel incident light beams leave the lenses on the concave side in the same parallel manner but more closely bundled. This bundling of light provides the magnifying effect for the human eye, because an increase of optical information reaches the retina having passed through the pupil (of a given diameter) of the eye of the beholder.
Nevertheless, a magnifying effect of known telescopic spectacles having a large visual field is small. For example the DE G 81 21 262.3 telescopic spectacles a magnifying effect of only 1.15. These telescopic spectacles, 1.15 of G 81 21 262.3, have a refractive index of 1.50, a length diameter of 0.04 m (40 mm), an axial thickness of 0.02 m (20 mm), a spherical front surface curvature of 0.05 m (+10.0 Dpt) and a spherical rear surface curvature of 0.0433 meters (-11.5473 Dpt). The resulting visual field for the eyes of an observer is 1300 m at a distance of 1000 m, i.e. comprising about 66.. The small magnifying effect of telescopic eyeglasses like G 81 21 262.3 is not very susceptible to industrial application, although the visual field is large.
Former known afocal telescopes, for example U.S. Pat. No. 346,002 (Bennet et al, 1944) also have perceptible magnifying effects. However, due to the tubular shape and the apertures and diaphragms inherent in this shape, they have only a small visual field. Furthermore, telescopes as in U.S. Pat. No. 2,346,002 due to their lengths, their high weight and their unwieldiness, can never be worn in conventional spectacle frames. Therefore, telescopes as taught by Bennet et al are not susceptible to industrial application in the sense of the present invention.
In conclusion, up to now, binocular spectacles do not exist, which produce an appreciable magnifying effect for human eyes and at the same time an habitual or at least a relatively large visual field.
Furthermore, an illuminating headpiece for spectacles including secondary magnifying lenses (magnification insert) is known from U.S. Pat. No. 3,592,525 (Schultz 1971). These spectacles have indeed a pronounced magnification because of the tube-shaped magnification insert for the working distance, i.e. for near vision, and simultaneously a large usual field of vision in the remaining region of the spectacle lenses. But these spectacles as well as other similar spectacles (for example Kheeler spectacles for ophthalmologists, are not binoculars for distance because they are made for a working distance of 20 cm. Therefore, the tube axes of the magnification portion are explicitly convergent (see Bennet et al, FIG. 2 and text). Finally the magnification inserts are focal and not afocal, because focusing for the working distance by a (additional refractive power) of +5.0 Dpt is required. This is necessary so that the user perceives a sharp and magnified picture through these inserts. The spectacles according to the U.S. Pat. No.. 3,592,525 for dentists and ophthalmologists and similar spectacles (Kheeler) do not yield a sharp and magnified vision for people having a normal eyesight.
Due to the existing apertures and diaphragms of the magnification inserts, the resulting visual field is small, and amounts to roughly 12 at the near distance for the Kheeler spectacles, and for the Schultz spectacles it is even smaller.
The user of the Schultz spectacles (U.S. 3,592,525) has no binocular distance vision due to the convergent adjustment of the lens axes. Because of the near focusing (+5.0 Dpt) of the magnification insert, a person having normal eyesight cannot see even with approximate sharpness monocularly nor binocularly, rather he perceives only completely blurred images which are also thus not magnified in the true sense of the word. In conclusion, binoculars for distance vision in spectacle frames do not exist, at least such having a large visual field and which are susceptible of industrial application.
The present application is based on our own four Utility Model applications in the Federal Republic of Germany:
G 88 04 514.3 (filing date Apr. 4, 1989), PA1 G 88 07 504.4 (filing date June 9, 1988), PA1 G 88 14 084.9 (filing date Nov. 10, 1988) PA1 G 88 14 085.7 (filing date Nov. 10, 1988) PA1 EP 102293.7 (filing date Feb. 10, 1989) and claims their priorities.